1. Technical Field
Exemplary embodiments relate generally to semiconductor memory devices, and more particularly to methods of operating nonvolatile memory devices.
2. Discussion of the Related Art
Semiconductor memory devices may be volatile or nonvolatile. Volatile semiconductor memory devices perform read and write operations at a high speed, while contents stored therein may be lost at power-off. Nonvolatile semiconductor memory devices may retain contents stored therein even at power-off. Nonvolatile semiconductor memory devices may be used to store contents that must be retained regardless of whether they are powered.
Flash memory devices are typically nonvolatile semiconductor memory devices. Flash memory devices may be used as a voice and image data storing medium for information appliances, such as a computer, a cellular phone, a PDA, a digital camera, a camcorder, a voice recorder, an MP3 player, a handheld PC, a game machine, a facsimile, a scanner, a printer, and the like.
Recently, semiconductor memory devices having memory cells that are stacked in three dimensions have been researched to improve integrity of the semiconductor memory devices. However, increases in storage capacity may cause various problems such as a soft erase caused by word-line coupling.